Semiconductor devices are typically designed by connecting circuit and logic devices in arrangements to perform specific functions. To fabricate these arrangements, the circuits are represented as physical arrangements of geometric shapes, often referred to as a layout, on a variety of layers to be fabricated on the semiconductor device. The geometric shapes alone, or in combination with other shapes on other layers create the various circuit elements and other device elements such as wells, diffusion areas, oxidation regions, transistors, capacitors, interconnection signals, contacts, vias, passivation openings, and the like.
Generally, these geometric shapes are created using Computer Aided Design (CAD) systems to draw the shapes and create the circuit elements either by hand or in an automated fashion. With the layout created and stored in a database, the semiconductor device may be manufactured based on the layout database.
Photolithography, also termed optical lithography, is a well known process for transferring geometric shapes onto the surface of a semiconductor wafer. In the optical lithography process, a series of masks are created, which may be used for forming the various layers on the wafer. Masks may be formed on a sheet of transparent glass or quartz with the shapes from the layout database formed as opaque regions on the transparent sheet. The mask is positioned above the wafer and light is shone through the mask to expose areas of the wafer corresponding to the transparent regions of the mask and leave unexposed areas of the wafer corresponding to the opaque regions of the mask. A photoresist layer may be formed on a surface of the semiconductor wafer prior to this exposure. Areas of the photoresist layer exposed to the light may change state such that some of the photoresist may be removed to form a pattern of photoresist on the wafer that substantially matches the pattern on the mask. This pattern can then be used for etching underlying regions of the wafer or depositing additional layers in the areas not covered by photoresist. This process may be repeated for many masks and processing layers on the wafer until the semiconductor devices on the wafer are fully formed.
Semiconductor devices are continually becoming more complex with millions of devices, and their accompanying interconnect signals, possible on any given semiconductor device. Furthermore, layout databases may contain dozens of different layers for creating these devices and interconnect signals. As a result, layout databases have become extremely large and unwieldy to communicate between computers and to process the data within the layout database.
There is a need for systems and methods to modify these layout databases in a fashion to enhance the layout database for additional processing that may be required on the database, as well as to reduce the size of the database.